metamer

Main Entry: meta·mer
Pronunciation: 'met-&-"m&r
Function: noun
1 : a chemical compound that is metameric with one or more others
2 : either of two colors of different spectral composition that appear identical to the eye of a single observer under some lighting conditions but different under others or that underconstant lighting conditions appear identical to some observers and different to others

metamer met·a·mer (mět'ə-mər)
n.

1. A compound that contains the same number and type of atoms as other compounds but with a different distribution of radicals.

2. A color that appears to the eye to be identical to another color but which in fact has a different spectral composition.